Astronauts Go On Spacewalk to Fix Space Station Ammonia Leak

Two American astronauts went on a six hour-long spacewalk Saturday to fix an ammonia leak outside the International Space Station.

Astronauts Chris Cassidy and Tom Marshburn removed a 113-kilogram box housing a faulty pump and replaced it with a spare.

NASA engineers say they do not see any new signs of a leak and are very happy. But they say it could take months before they know if the problem is permanently fixed.

Ammonia is used to cool the space station's power system. The crew first saw the leak Thursday when they reported flakes of ammonia drifting into space. NASA says the situation was serious but says the crew was never in any danger.